* [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice
@ 2022-01-25 7:51 Kees Cook
2022-01-25 8:24 ` Masahiro Yamada
2022-01-28 20:58 ` Nathan Chancellor
0 siblings, 2 replies; 6+ messages in thread
From: Kees Cook @ 2022-01-25 7:51 UTC (permalink / raw)
To: Andrew Morton
Cc: Kees Cook, Arnd Bergmann, Masahiro Yamada, Nick Desaulniers,
Tetsuo Handa, Nathan Chancellor, Peter Zijlstra, Isabella Basso,
linux-kernel, linux-hardening
Currently it's not possible to enable DEBUG_INFO for an all*config build,
since it is marked as "depends on !COMPILE_TEST". This generally makes
sense because a debug build of an all*config target ends up taking much
longer and the output is much larger. Having this be "default off" makes
sense. However, there are cases where enabling DEBUG_INFO for such builds
is useful for doing treewide A/B comparisons of build options, etc.
Make DEBUG_INFO selectable from any of the DWARF version choice options,
with DEBUG_INFO_NONE being the default for COMPILE_TEST. The mutually
exclusive relationship between DWARF5 and BTF must be inverted, but the
result remains the same. Additionally moves DEBUG_KERNEL and DEBUG_MISC
up to the top of the menu because they were enabling features _above_
it, making it weird to navigate menuconfig.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v1: https://lore.kernel.org/lkml/20211210000910.3597609-1-keescook@chromium.org
v2: https://lore.kernel.org/lkml/20220121001204.4023842-1-keescook@chromium.org
v3: - rebase to v5.17-rc1
---
lib/Kconfig.debug | 140 +++++++++++++++++++++++++---------------------
1 file changed, 75 insertions(+), 65 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 14b89aa37c5c..1290e0906236 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -208,20 +208,88 @@ config DEBUG_BUGVERBOSE
endmenu # "printk and dmesg options"
+config DEBUG_KERNEL
+ bool "Kernel debugging"
+ help
+ Say Y here if you are developing drivers or trying to debug and
+ identify kernel problems.
+
+config DEBUG_MISC
+ bool "Miscellaneous debug code"
+ default DEBUG_KERNEL
+ depends on DEBUG_KERNEL
+ help
+ Say Y here if you need to enable miscellaneous debug code that should
+ be under a more specific debug option but isn't.
+
menu "Compile-time checks and compiler options"
config DEBUG_INFO
- bool "Compile the kernel with debug info"
- depends on DEBUG_KERNEL && !COMPILE_TEST
+ bool
help
- If you say Y here the resulting kernel image will include
- debugging info resulting in a larger kernel image.
+ A kernel debug info option other than "None" has been selected
+ in the "Debug information" choice below, indicating that debug
+ information will be generated for build targets.
+
+choice
+ prompt "Debug information"
+ depends on DEBUG_KERNEL
+ default DEBUG_INFO_NONE if COMPILE_TEST
+ help
+ Selecting something other than "None" results in a kernel image
+ that will include debugging info resulting in a larger kernel image.
This adds debug symbols to the kernel and modules (gcc -g), and
is needed if you intend to use kernel crashdump or binary object
tools like crash, kgdb, LKCD, gdb, etc on the kernel.
- Say Y here only if you plan to debug the kernel.
- If unsure, say N.
+ Choose which version of DWARF debug info to emit. If unsure,
+ select "Toolchain default".
+
+config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
+ bool "Rely on the toolchain's implicit default DWARF version"
+ select DEBUG_INFO
+ help
+ The implicit default version of DWARF debug info produced by a
+ toolchain changes over time.
+
+ This can break consumers of the debug info that haven't upgraded to
+ support newer revisions, and prevent testing newer versions, but
+ those should be less common scenarios.
+
+config DEBUG_INFO_DWARF4
+ bool "Generate DWARF Version 4 debuginfo"
+ select DEBUG_INFO
+ help
+ Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
+
+ If you have consumers of DWARF debug info that are not ready for
+ newer revisions of DWARF, you may wish to choose this or have your
+ config select this.
+
+config DEBUG_INFO_DWARF5
+ bool "Generate DWARF Version 5 debuginfo"
+ select DEBUG_INFO
+ depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
+ help
+ Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
+ 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
+ draft features until 7.0), and gdb 8.0+.
+
+ Changes to the structure of debug info in Version 5 allow for around
+ 15-18% savings in resulting image and debug info section sizes as
+ compared to DWARF Version 4. DWARF Version 5 standardizes previous
+ extensions such as accelerators for symbol indexing and the format
+ for fission (.dwo/.dwp) files. Users may not want to select this
+ config if they rely on tooling that has not yet been updated to
+ support DWARF Version 5.
+
+config DEBUG_INFO_NONE
+ bool "Disable debug information"
+ help
+ Do not build the kernel with debugging information, which will
+ result in a faster and smaller build.
+
+endchoice # "Debug information"
if DEBUG_INFO
@@ -267,56 +335,12 @@ config DEBUG_INFO_SPLIT
to know about the .dwo files and include them.
Incompatible with older versions of ccache.
-choice
- prompt "DWARF version"
- help
- Which version of DWARF debug info to emit.
-
-config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
- bool "Rely on the toolchain's implicit default DWARF version"
- help
- The implicit default version of DWARF debug info produced by a
- toolchain changes over time.
-
- This can break consumers of the debug info that haven't upgraded to
- support newer revisions, and prevent testing newer versions, but
- those should be less common scenarios.
-
- If unsure, say Y.
-
-config DEBUG_INFO_DWARF4
- bool "Generate DWARF Version 4 debuginfo"
- help
- Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
-
- If you have consumers of DWARF debug info that are not ready for
- newer revisions of DWARF, you may wish to choose this or have your
- config select this.
-
-config DEBUG_INFO_DWARF5
- bool "Generate DWARF Version 5 debuginfo"
- depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
- depends on !DEBUG_INFO_BTF
- help
- Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
- 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
- draft features until 7.0), and gdb 8.0+.
-
- Changes to the structure of debug info in Version 5 allow for around
- 15-18% savings in resulting image and debug info section sizes as
- compared to DWARF Version 4. DWARF Version 5 standardizes previous
- extensions such as accelerators for symbol indexing and the format
- for fission (.dwo/.dwp) files. Users may not want to select this
- config if they rely on tooling that has not yet been updated to
- support DWARF Version 5.
-
-endchoice # "DWARF version"
-
config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
depends on BPF_SYSCALL
+ depends on !DEBUG_INFO_DWARF5
help
Generate deduplicated BTF type information from DWARF debug info.
Turning this on expects presence of pahole tool, which will convert
@@ -585,20 +609,6 @@ source "lib/Kconfig.kcsan"
endmenu
-config DEBUG_KERNEL
- bool "Kernel debugging"
- help
- Say Y here if you are developing drivers or trying to debug and
- identify kernel problems.
-
-config DEBUG_MISC
- bool "Miscellaneous debug code"
- default DEBUG_KERNEL
- depends on DEBUG_KERNEL
- help
- Say Y here if you need to enable miscellaneous debug code that should
- be under a more specific debug option but isn't.
-
menu "Networking Debugging"
source "net/Kconfig.debug"
--
2.30.2
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice
2022-01-25 7:51 [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice Kees Cook
@ 2022-01-25 8:24 ` Masahiro Yamada
2022-01-28 20:58 ` Nathan Chancellor
1 sibling, 0 replies; 6+ messages in thread
From: Masahiro Yamada @ 2022-01-25 8:24 UTC (permalink / raw)
To: Kees Cook
Cc: Andrew Morton, Arnd Bergmann, Nick Desaulniers, Tetsuo Handa,
Nathan Chancellor, Peter Zijlstra, Isabella Basso,
Linux Kernel Mailing List, linux-hardening
On Tue, Jan 25, 2022 at 4:51 PM Kees Cook <keescook@chromium.org> wrote:
>
> Currently it's not possible to enable DEBUG_INFO for an all*config build,
> since it is marked as "depends on !COMPILE_TEST". This generally makes
> sense because a debug build of an all*config target ends up taking much
> longer and the output is much larger. Having this be "default off" makes
> sense. However, there are cases where enabling DEBUG_INFO for such builds
> is useful for doing treewide A/B comparisons of build options, etc.
>
> Make DEBUG_INFO selectable from any of the DWARF version choice options,
> with DEBUG_INFO_NONE being the default for COMPILE_TEST. The mutually
> exclusive relationship between DWARF5 and BTF must be inverted, but the
> result remains the same. Additionally moves DEBUG_KERNEL and DEBUG_MISC
> up to the top of the menu because they were enabling features _above_
> it, making it weird to navigate menuconfig.
>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v1: https://lore.kernel.org/lkml/20211210000910.3597609-1-keescook@chromium.org
> v2: https://lore.kernel.org/lkml/20220121001204.4023842-1-keescook@chromium.org
> v3: - rebase to v5.17-rc1
> ---
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice
2022-01-25 7:51 [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice Kees Cook
2022-01-25 8:24 ` Masahiro Yamada
@ 2022-01-28 20:58 ` Nathan Chancellor
2022-01-28 21:27 ` Kees Cook
1 sibling, 1 reply; 6+ messages in thread
From: Nathan Chancellor @ 2022-01-28 20:58 UTC (permalink / raw)
To: Kees Cook
Cc: Andrew Morton, Arnd Bergmann, Masahiro Yamada, Nick Desaulniers,
Tetsuo Handa, Peter Zijlstra, Isabella Basso, linux-kernel,
linux-hardening
Hi Kees,
On Mon, Jan 24, 2022 at 11:51:26PM -0800, Kees Cook wrote:
> Currently it's not possible to enable DEBUG_INFO for an all*config build,
> since it is marked as "depends on !COMPILE_TEST". This generally makes
> sense because a debug build of an all*config target ends up taking much
> longer and the output is much larger. Having this be "default off" makes
> sense. However, there are cases where enabling DEBUG_INFO for such builds
> is useful for doing treewide A/B comparisons of build options, etc.
>
> Make DEBUG_INFO selectable from any of the DWARF version choice options,
> with DEBUG_INFO_NONE being the default for COMPILE_TEST. The mutually
> exclusive relationship between DWARF5 and BTF must be inverted, but the
> result remains the same. Additionally moves DEBUG_KERNEL and DEBUG_MISC
> up to the top of the menu because they were enabling features _above_
> it, making it weird to navigate menuconfig.
>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v1: https://lore.kernel.org/lkml/20211210000910.3597609-1-keescook@chromium.org
> v2: https://lore.kernel.org/lkml/20220121001204.4023842-1-keescook@chromium.org
> v3: - rebase to v5.17-rc1
> ---
> lib/Kconfig.debug | 140 +++++++++++++++++++++++++---------------------
> 1 file changed, 75 insertions(+), 65 deletions(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 14b89aa37c5c..1290e0906236 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -208,20 +208,88 @@ config DEBUG_BUGVERBOSE
>
> endmenu # "printk and dmesg options"
>
> +config DEBUG_KERNEL
> + bool "Kernel debugging"
> + help
> + Say Y here if you are developing drivers or trying to debug and
> + identify kernel problems.
> +
> +config DEBUG_MISC
> + bool "Miscellaneous debug code"
> + default DEBUG_KERNEL
> + depends on DEBUG_KERNEL
> + help
> + Say Y here if you need to enable miscellaneous debug code that should
> + be under a more specific debug option but isn't.
> +
> menu "Compile-time checks and compiler options"
>
> config DEBUG_INFO
> - bool "Compile the kernel with debug info"
> - depends on DEBUG_KERNEL && !COMPILE_TEST
> + bool
> help
> - If you say Y here the resulting kernel image will include
> - debugging info resulting in a larger kernel image.
> + A kernel debug info option other than "None" has been selected
> + in the "Debug information" choice below, indicating that debug
> + information will be generated for build targets.
> +
> +choice
> + prompt "Debug information"
> + depends on DEBUG_KERNEL
> + default DEBUG_INFO_NONE if COMPILE_TEST
I apologize for not bringing this up sooner in review (especially with
my tag) but I wanted to make sure this change is intentional.
Prior to this commit, we would have to explicitly enable DEBUG_INFO
after turning on DEBUG_KERNEL (i.e. DEBUG_KERNEL would not select
DEBUG_INFO).
Now, DEBUG_INFO automatically gets turned on with DEBUG_KERNEL because
of the depends plus the default for the choice. Is this intentional?
For example, with x86_64_defconfig:
mainline:
$ make mrproper defconfig && rg DEBUG_INFO .config
4571:# CONFIG_DEBUG_INFO is not set
next-20220128:
$ make mrproper defconfig && rg DEBUG_INFO .config
4573:CONFIG_DEBUG_INFO=y
4574:CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
4575:# CONFIG_DEBUG_INFO_DWARF4 is not set
4576:# CONFIG_DEBUG_INFO_DWARF5 is not set
4577:# CONFIG_DEBUG_INFO_NONE is not set
4578:# CONFIG_DEBUG_INFO_REDUCED is not set
4579:# CONFIG_DEBUG_INFO_COMPRESSED is not set
4580:# CONFIG_DEBUG_INFO_SPLIT is not set
As far as I can tell, this will have a big impact on everyone's binary
and modules size that either enables DEBUG_KERNEL or EXPERT (which
selects DEBUG_KERNEL), which is a lot of configs.
$ for file in $(rg -l "CONFIG_(DEBUG_KERNEL|EXPERT)" arch/*/configs); do rg DEBUG_INFO $file &>/dev/null || echo $file; done |& wc -l
170
If this change is intentional, then it probably warrants more of an
explicit callout in the commit message. I only noticed this because the
vmlinux for the multi_v7_defconfig kernel I build for my Raspberry Pi 3
went from 32.44 MB to 262.75 MB.
Cheers,
Nathan
> + help
> + Selecting something other than "None" results in a kernel image
> + that will include debugging info resulting in a larger kernel image.
> This adds debug symbols to the kernel and modules (gcc -g), and
> is needed if you intend to use kernel crashdump or binary object
> tools like crash, kgdb, LKCD, gdb, etc on the kernel.
> - Say Y here only if you plan to debug the kernel.
>
> - If unsure, say N.
> + Choose which version of DWARF debug info to emit. If unsure,
> + select "Toolchain default".
> +
> +config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
> + bool "Rely on the toolchain's implicit default DWARF version"
> + select DEBUG_INFO
> + help
> + The implicit default version of DWARF debug info produced by a
> + toolchain changes over time.
> +
> + This can break consumers of the debug info that haven't upgraded to
> + support newer revisions, and prevent testing newer versions, but
> + those should be less common scenarios.
> +
> +config DEBUG_INFO_DWARF4
> + bool "Generate DWARF Version 4 debuginfo"
> + select DEBUG_INFO
> + help
> + Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> +
> + If you have consumers of DWARF debug info that are not ready for
> + newer revisions of DWARF, you may wish to choose this or have your
> + config select this.
> +
> +config DEBUG_INFO_DWARF5
> + bool "Generate DWARF Version 5 debuginfo"
> + select DEBUG_INFO
> + depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
> + help
> + Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> + 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
> + draft features until 7.0), and gdb 8.0+.
> +
> + Changes to the structure of debug info in Version 5 allow for around
> + 15-18% savings in resulting image and debug info section sizes as
> + compared to DWARF Version 4. DWARF Version 5 standardizes previous
> + extensions such as accelerators for symbol indexing and the format
> + for fission (.dwo/.dwp) files. Users may not want to select this
> + config if they rely on tooling that has not yet been updated to
> + support DWARF Version 5.
> +
> +config DEBUG_INFO_NONE
> + bool "Disable debug information"
> + help
> + Do not build the kernel with debugging information, which will
> + result in a faster and smaller build.
> +
> +endchoice # "Debug information"
>
> if DEBUG_INFO
>
> @@ -267,56 +335,12 @@ config DEBUG_INFO_SPLIT
> to know about the .dwo files and include them.
> Incompatible with older versions of ccache.
>
> -choice
> - prompt "DWARF version"
> - help
> - Which version of DWARF debug info to emit.
> -
> -config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
> - bool "Rely on the toolchain's implicit default DWARF version"
> - help
> - The implicit default version of DWARF debug info produced by a
> - toolchain changes over time.
> -
> - This can break consumers of the debug info that haven't upgraded to
> - support newer revisions, and prevent testing newer versions, but
> - those should be less common scenarios.
> -
> - If unsure, say Y.
> -
> -config DEBUG_INFO_DWARF4
> - bool "Generate DWARF Version 4 debuginfo"
> - help
> - Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> -
> - If you have consumers of DWARF debug info that are not ready for
> - newer revisions of DWARF, you may wish to choose this or have your
> - config select this.
> -
> -config DEBUG_INFO_DWARF5
> - bool "Generate DWARF Version 5 debuginfo"
> - depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
> - depends on !DEBUG_INFO_BTF
> - help
> - Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> - 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
> - draft features until 7.0), and gdb 8.0+.
> -
> - Changes to the structure of debug info in Version 5 allow for around
> - 15-18% savings in resulting image and debug info section sizes as
> - compared to DWARF Version 4. DWARF Version 5 standardizes previous
> - extensions such as accelerators for symbol indexing and the format
> - for fission (.dwo/.dwp) files. Users may not want to select this
> - config if they rely on tooling that has not yet been updated to
> - support DWARF Version 5.
> -
> -endchoice # "DWARF version"
> -
> config DEBUG_INFO_BTF
> bool "Generate BTF typeinfo"
> depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
> depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
> depends on BPF_SYSCALL
> + depends on !DEBUG_INFO_DWARF5
> help
> Generate deduplicated BTF type information from DWARF debug info.
> Turning this on expects presence of pahole tool, which will convert
> @@ -585,20 +609,6 @@ source "lib/Kconfig.kcsan"
>
> endmenu
>
> -config DEBUG_KERNEL
> - bool "Kernel debugging"
> - help
> - Say Y here if you are developing drivers or trying to debug and
> - identify kernel problems.
> -
> -config DEBUG_MISC
> - bool "Miscellaneous debug code"
> - default DEBUG_KERNEL
> - depends on DEBUG_KERNEL
> - help
> - Say Y here if you need to enable miscellaneous debug code that should
> - be under a more specific debug option but isn't.
> -
> menu "Networking Debugging"
>
> source "net/Kconfig.debug"
> --
> 2.30.2
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice
2022-01-28 20:58 ` Nathan Chancellor
@ 2022-01-28 21:27 ` Kees Cook
0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2022-01-28 21:27 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Andrew Morton, Arnd Bergmann, Masahiro Yamada, Nick Desaulniers,
Tetsuo Handa, Peter Zijlstra, Isabella Basso, linux-kernel,
linux-hardening
On Fri, Jan 28, 2022 at 01:58:19PM -0700, Nathan Chancellor wrote:
> Hi Kees,
>
> On Mon, Jan 24, 2022 at 11:51:26PM -0800, Kees Cook wrote:
> > Currently it's not possible to enable DEBUG_INFO for an all*config build,
> > since it is marked as "depends on !COMPILE_TEST". This generally makes
> > sense because a debug build of an all*config target ends up taking much
> > longer and the output is much larger. Having this be "default off" makes
> > sense. However, there are cases where enabling DEBUG_INFO for such builds
> > is useful for doing treewide A/B comparisons of build options, etc.
> >
> > Make DEBUG_INFO selectable from any of the DWARF version choice options,
> > with DEBUG_INFO_NONE being the default for COMPILE_TEST. The mutually
> > exclusive relationship between DWARF5 and BTF must be inverted, but the
> > result remains the same. Additionally moves DEBUG_KERNEL and DEBUG_MISC
> > up to the top of the menu because they were enabling features _above_
> > it, making it weird to navigate menuconfig.
> >
> > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> > Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > v1: https://lore.kernel.org/lkml/20211210000910.3597609-1-keescook@chromium.org
> > v2: https://lore.kernel.org/lkml/20220121001204.4023842-1-keescook@chromium.org
> > v3: - rebase to v5.17-rc1
> > ---
> > lib/Kconfig.debug | 140 +++++++++++++++++++++++++---------------------
> > 1 file changed, 75 insertions(+), 65 deletions(-)
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 14b89aa37c5c..1290e0906236 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -208,20 +208,88 @@ config DEBUG_BUGVERBOSE
> >
> > endmenu # "printk and dmesg options"
> >
> > +config DEBUG_KERNEL
> > + bool "Kernel debugging"
> > + help
> > + Say Y here if you are developing drivers or trying to debug and
> > + identify kernel problems.
> > +
> > +config DEBUG_MISC
> > + bool "Miscellaneous debug code"
> > + default DEBUG_KERNEL
> > + depends on DEBUG_KERNEL
> > + help
> > + Say Y here if you need to enable miscellaneous debug code that should
> > + be under a more specific debug option but isn't.
> > +
> > menu "Compile-time checks and compiler options"
> >
> > config DEBUG_INFO
> > - bool "Compile the kernel with debug info"
> > - depends on DEBUG_KERNEL && !COMPILE_TEST
> > + bool
> > help
> > - If you say Y here the resulting kernel image will include
> > - debugging info resulting in a larger kernel image.
> > + A kernel debug info option other than "None" has been selected
> > + in the "Debug information" choice below, indicating that debug
> > + information will be generated for build targets.
> > +
> > +choice
> > + prompt "Debug information"
> > + depends on DEBUG_KERNEL
> > + default DEBUG_INFO_NONE if COMPILE_TEST
>
> I apologize for not bringing this up sooner in review (especially with
> my tag) but I wanted to make sure this change is intentional.
>
> Prior to this commit, we would have to explicitly enable DEBUG_INFO
> after turning on DEBUG_KERNEL (i.e. DEBUG_KERNEL would not select
> DEBUG_INFO).
>
> Now, DEBUG_INFO automatically gets turned on with DEBUG_KERNEL because
> of the depends plus the default for the choice. Is this intentional?
Oh, er, no. I think this was an oversight when I tried to adapt this to
Masahiro's suggestions. I will go fix this up.
> For example, with x86_64_defconfig:
>
> mainline:
>
> $ make mrproper defconfig && rg DEBUG_INFO .config
> 4571:# CONFIG_DEBUG_INFO is not set
>
> next-20220128:
>
> $ make mrproper defconfig && rg DEBUG_INFO .config
> 4573:CONFIG_DEBUG_INFO=y
> 4574:CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
> 4575:# CONFIG_DEBUG_INFO_DWARF4 is not set
> 4576:# CONFIG_DEBUG_INFO_DWARF5 is not set
> 4577:# CONFIG_DEBUG_INFO_NONE is not set
> 4578:# CONFIG_DEBUG_INFO_REDUCED is not set
> 4579:# CONFIG_DEBUG_INFO_COMPRESSED is not set
> 4580:# CONFIG_DEBUG_INFO_SPLIT is not set
>
> As far as I can tell, this will have a big impact on everyone's binary
> and modules size that either enables DEBUG_KERNEL or EXPERT (which
> selects DEBUG_KERNEL), which is a lot of configs.
Yes, agreed, it's a huge size difference! :)
-Kees
>
> $ for file in $(rg -l "CONFIG_(DEBUG_KERNEL|EXPERT)" arch/*/configs); do rg DEBUG_INFO $file &>/dev/null || echo $file; done |& wc -l
> 170
>
> If this change is intentional, then it probably warrants more of an
> explicit callout in the commit message. I only noticed this because the
> vmlinux for the multi_v7_defconfig kernel I build for my Raspberry Pi 3
> went from 32.44 MB to 262.75 MB.
>
> Cheers,
> Nathan
>
> > + help
> > + Selecting something other than "None" results in a kernel image
> > + that will include debugging info resulting in a larger kernel image.
> > This adds debug symbols to the kernel and modules (gcc -g), and
> > is needed if you intend to use kernel crashdump or binary object
> > tools like crash, kgdb, LKCD, gdb, etc on the kernel.
> > - Say Y here only if you plan to debug the kernel.
> >
> > - If unsure, say N.
> > + Choose which version of DWARF debug info to emit. If unsure,
> > + select "Toolchain default".
> > +
> > +config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
> > + bool "Rely on the toolchain's implicit default DWARF version"
> > + select DEBUG_INFO
> > + help
> > + The implicit default version of DWARF debug info produced by a
> > + toolchain changes over time.
> > +
> > + This can break consumers of the debug info that haven't upgraded to
> > + support newer revisions, and prevent testing newer versions, but
> > + those should be less common scenarios.
> > +
> > +config DEBUG_INFO_DWARF4
> > + bool "Generate DWARF Version 4 debuginfo"
> > + select DEBUG_INFO
> > + help
> > + Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> > +
> > + If you have consumers of DWARF debug info that are not ready for
> > + newer revisions of DWARF, you may wish to choose this or have your
> > + config select this.
> > +
> > +config DEBUG_INFO_DWARF5
> > + bool "Generate DWARF Version 5 debuginfo"
> > + select DEBUG_INFO
> > + depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
> > + help
> > + Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> > + 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
> > + draft features until 7.0), and gdb 8.0+.
> > +
> > + Changes to the structure of debug info in Version 5 allow for around
> > + 15-18% savings in resulting image and debug info section sizes as
> > + compared to DWARF Version 4. DWARF Version 5 standardizes previous
> > + extensions such as accelerators for symbol indexing and the format
> > + for fission (.dwo/.dwp) files. Users may not want to select this
> > + config if they rely on tooling that has not yet been updated to
> > + support DWARF Version 5.
> > +
> > +config DEBUG_INFO_NONE
> > + bool "Disable debug information"
> > + help
> > + Do not build the kernel with debugging information, which will
> > + result in a faster and smaller build.
> > +
> > +endchoice # "Debug information"
> >
> > if DEBUG_INFO
> >
> > @@ -267,56 +335,12 @@ config DEBUG_INFO_SPLIT
> > to know about the .dwo files and include them.
> > Incompatible with older versions of ccache.
> >
> > -choice
> > - prompt "DWARF version"
> > - help
> > - Which version of DWARF debug info to emit.
> > -
> > -config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
> > - bool "Rely on the toolchain's implicit default DWARF version"
> > - help
> > - The implicit default version of DWARF debug info produced by a
> > - toolchain changes over time.
> > -
> > - This can break consumers of the debug info that haven't upgraded to
> > - support newer revisions, and prevent testing newer versions, but
> > - those should be less common scenarios.
> > -
> > - If unsure, say Y.
> > -
> > -config DEBUG_INFO_DWARF4
> > - bool "Generate DWARF Version 4 debuginfo"
> > - help
> > - Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> > -
> > - If you have consumers of DWARF debug info that are not ready for
> > - newer revisions of DWARF, you may wish to choose this or have your
> > - config select this.
> > -
> > -config DEBUG_INFO_DWARF5
> > - bool "Generate DWARF Version 5 debuginfo"
> > - depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
> > - depends on !DEBUG_INFO_BTF
> > - help
> > - Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> > - 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
> > - draft features until 7.0), and gdb 8.0+.
> > -
> > - Changes to the structure of debug info in Version 5 allow for around
> > - 15-18% savings in resulting image and debug info section sizes as
> > - compared to DWARF Version 4. DWARF Version 5 standardizes previous
> > - extensions such as accelerators for symbol indexing and the format
> > - for fission (.dwo/.dwp) files. Users may not want to select this
> > - config if they rely on tooling that has not yet been updated to
> > - support DWARF Version 5.
> > -
> > -endchoice # "DWARF version"
> > -
> > config DEBUG_INFO_BTF
> > bool "Generate BTF typeinfo"
> > depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
> > depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
> > depends on BPF_SYSCALL
> > + depends on !DEBUG_INFO_DWARF5
> > help
> > Generate deduplicated BTF type information from DWARF debug info.
> > Turning this on expects presence of pahole tool, which will convert
> > @@ -585,20 +609,6 @@ source "lib/Kconfig.kcsan"
> >
> > endmenu
> >
> > -config DEBUG_KERNEL
> > - bool "Kernel debugging"
> > - help
> > - Say Y here if you are developing drivers or trying to debug and
> > - identify kernel problems.
> > -
> > -config DEBUG_MISC
> > - bool "Miscellaneous debug code"
> > - default DEBUG_KERNEL
> > - depends on DEBUG_KERNEL
> > - help
> > - Say Y here if you need to enable miscellaneous debug code that should
> > - be under a more specific debug option but isn't.
> > -
> > menu "Networking Debugging"
> >
> > source "net/Kconfig.debug"
> > --
> > 2.30.2
> >
> >
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice
@ 2022-01-25 21:09 ` kernel test robot
0 siblings, 0 replies; 6+ messages in thread
From: kernel test robot @ 2022-01-25 21:09 UTC (permalink / raw)
Cc: kbuild-all, llvm
In-Reply-To: <20220125075126.891825-1-keescook@chromium.org>
References: <20220125075126.891825-1-keescook@chromium.org>
TO: Kees Cook <keescook@chromium.org>
TO: Andrew Morton <akpm@linux-foundation.org>
CC: Linux Memory Management List <linux-mm@kvack.org>
CC: Kees Cook <keescook@chromium.org>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Masahiro Yamada <masahiroy@kernel.org>
CC: Nick Desaulniers <ndesaulniers@google.com>
CC: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
CC: Nathan Chancellor <nathan@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Isabella Basso <isabbasso@riseup.net>
Hi Kees,
I love your patch! Yet something to improve:
[auto build test ERROR on linus/master]
[also build test ERROR on v5.17-rc1 next-20220125]
[cannot apply to kees/for-next/pstore soc/for-next hnaz-mm/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Kees-Cook/Kconfig-debug-Make-DEBUG_INFO-selectable-from-a-choice/20220125-170038
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git dd81e1c7d5fb126e5fbc5c9e334d7b3ec29a16a0
config: riscv-buildonly-randconfig-r001-20220124 (https://download.01.org/0day-ci/archive/20220126/202201260410.RSiRayDu-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 997e128e2a78f5a5434fc75997441ae1ee76f8a4)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install riscv cross compiling tool for clang build
# apt-get install binutils-riscv64-linux-gnu
# https://github.com/0day-ci/linux/commit/1046f1c82b089b9cde35f6fcb0b3f34f53a90fa4
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Kees-Cook/Kconfig-debug-Make-DEBUG_INFO-selectable-from-a-choice/20220125-170038
git checkout 1046f1c82b089b9cde35f6fcb0b3f34f53a90fa4
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
ld.lld: error: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
pahole: .tmp_vmlinux.btf: No such file or directory
>> ld.lld: error: .btf.vmlinux.bin.o: unknown file type
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-01-28 21:27 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-01-25 7:51 [PATCH v3] Kconfig.debug: Make DEBUG_INFO selectable from a choice Kees Cook
2022-01-25 8:24 ` Masahiro Yamada
2022-01-28 20:58 ` Nathan Chancellor
2022-01-28 21:27 ` Kees Cook
2022-01-25 21:09 kernel test robot
2022-01-25 21:09 ` kernel test robot
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